The Duramax LLY, LBZ, LMM Turbo - Diesel Insights

Today we return to the

turbo

shop. We're going to break down LLY, LBZ, LMM and show you everything you need to know about the Duramax line of variable vanes. (heavy metal music) Okay, so factory LLY

turbo

charger. This is the largest turbocharger on the variable vane trucks. So in 2004 and a half, 2005, it was the LLY. It has a 62.6 millimeter compressor measured here at the inducer, making it the largest compressor. It's also the only one that has a through turbine, so they're pretty easy to identify. The other cool thing about the LLY is that if you haven't seen the inside of one, here's a variable paddle pack.

There is an actuator in the center section that moves this ring, it is called the unison ring and that ensures that all the vanes move at the same time. And so you can change the geometry or the size of the nozzle on the vanes. So if you're at low speed or low load and you want to maintain a good compressor speed, a good turbine speed, you can close the vanes, which would be this position, and what this does is it creates this nozzle here, which is the space between the pallets. , smaller. And that increases the speed of the exhaust gases flowing through them, which speeds up the turbine a little bit, actually quite a bit.

And then as you get into higher load situations, you'll be able to equalize the back pressure, equalize the drive pressure, and maintain a good turbine shaft speed by moving the ring in unison. And all of that is controlled electronically by the engine management system. And voila, you have high gas flow, lots of horsepower and great movement. Some other situations that are kind of interesting that this is good for is turbine breakage. So you can close the vanes completely and if you're in tow mode or you have a high engine speed, you have a lot of exhaust gases pumping through the engine, with the vanes closed you create a lot of back pressure, 60, 70 pounds of back pressure. and what that does is cause a compression breakdown situation, so the engine floods and you can make quite a bit of power, 120, 150 horsepower quite easily, and stopping power, by closing these vanes.

So we do it in tune. I'll take this ring off in unison and show you one of the cool features of the LLY. Now, the LLY, LBZ and LLM are pretty similar turbochargers, I'm not going to go into each one specifically. The main difference is the measurement on the compressor and turbine wheels, the number of blades on the turbine wheel and then the height of the blades. And when I say paddle height I mean the height of this paddle measured this way, okay? By measuring the vanes in this way we obtain a 15 millimeter vane, which is the highest.

And what that means is that the LLY has the best-flowing exhaust section out of the box of any variable geometry turbocharger. Making it the most desirable for higher power users. In our experience, it's not really necessary until you get past the 640, 650 mark. There is a bit of a trade-off in low speed performance by using the stock unison ring compared to the LMM or LBZ turbocharger. Let's look at the wheels. I already told you, it is a 62.6 millimeter compressor. One, two, three, four, five, six, seven, eight, nine, 10, 11, 11 blade compressor. So it's the largest compressor of all the variable geometry turbochargers and it also has a pretty good size turbine, 65 by 62, it has a lot of blades and the blades are thick.

The thickness of the blade is about a millimeter in some spots and that's because when you have these nozzles like this you have areas of high gas velocity and high heat. So these vanes are made of inconel, the ring is inconel, the turbine shaft and the turbine head itself, not the shaft, the turbine head itself is inconel. And it has these thick blades to protect it from melting or being eroded by hot exhaust gases. So what is this for? Well again, similar to the LB7, we're at 530, 540 horsepower, I've seen some go as high as 550 with all the airflow mods.

The LLY did not receive the best breathing package from the factory, so it has a very restrictive intake. It has an EGR system that isn't that good, it has a Y bridge that sucks, it usually breaks, we see a lot of boost leaks on these trucks. But in a performance application where you address all of those things and have a good sealed system, the LLY turbocharger is the highest-performance original turbocharger in the Duramax. We don't really see too many faults in them. Actually, most of the failures are associated with EGR failures or with PCV problems or leaks, and what happens is that in this section of vanes, the oil starts to go through here, it burns, the vanes stick and the unison The ring stops moving and then you start getting turbocharger air codes, turbo vane position air codes, that kind of thing.

So when that happens, the turbocharger must be disassembled and cleaned. Otherwise we don't really see many overspeeds and overspeed failures, most tuners have found that you can't close the paddles very tight under high load. Typical boost range on this turbocharger, 35 PSI. Anything beyond that, you're entering the hot zone where you're pushing in a lot of hot air. You might be able to make 41 or 42 pounds of boost with this thing, but it won't make any more power than it does at 35 PSI. You really only risk failure of the turbocharger. In the video below, we'll show you what's involved in upgrading VBT turbochargers, taking them up to number 640 and beyond.

Thanks for watching. If you like these videos and want more information, check out the Diesel Tuners blog, DieselTunersBlog.com. (constant rock music)